Iran's president, Mahmoud Ahmadinejad, is planning to respond in person to intensifying international pressure over his country's controversial nuclear programme by taking his case directly to the United Nations security council in New York, it emerged yesterday.

Mr Ahmadinejad wanted to "defend the rights of the Iranian nation in exploiting peaceful nuclear energy," state TV quoted the Iranian government spokesman, Gholam Hossein Elham, as saying.

The president would attend if the security council holds a meeting on Iran's nuclear programme, the TV said. South Africa's ambassador, Dumisani Kumalo, whose country holds the council's rotating presidency, said that if Mr Ahmadinejad made a formal request, "it would be very difficult to deny him that opportunity". The US said it was not aware that any such request had been made.

Western countries, led by the US, insist that Iran's nuclear programme is a covert attempt to produce atomic weapons, a view reinforced by Tehran's continuing refusal to freeze uranium enrichment. Diplomatic efforts are under way to agree new UN sanctions to force it to comply.

The sensitivity of the issue is highlighted in a report today by a leading British foreign affairs think-tank warning that Israel - with its own large but undeclared nuclear arsenal - faces "dire and far-reaching consequences" if it takes military action against the Iranian programme.

Israeli airstrikes were possible, though "extremely risky", and Iran could retaliate with massive ballistic missile attacks on cities such as Tel Aviv or Haifa with "substantial" loss of life, says Yossi Mekelberg of Chatham House's Middle East programme. "An Israeli military operation against Iran would hurt Israel's long-term interests. It would be detrimental to Israel's overall security and the political and economic consequences would be dire and far-reaching," the report said. But it warned too that the Israelis may feel compelled to act if they believed Tehran was close to developing a nuclear bomb.

"Any military operation against Iran, as well as involving many casualties, would enhance the appeal of extremism in the Muslim world, inside and outside Iran, at the expense of the moderates."

If diplomacy failed, the report proposes that Israel could move to a policy of deterrence by openly declaring its own nuclear capability, mirroring the "balance of terror" that kept the peace between the west and the Soviet bloc in the cold war.

In Dubai, the French foreign minister Phillippe Douste-Blazy agreed that military action would destabilise the region and insisted that sanctions would have to be imposed on Iran.

Last December the security council imposed sanctions including a ban on the transfer of sensitive nuclear technology and threatened further measures if Iran failed to suspend enrichment. The five permanent council members plus Germany are now consulting on new proposals including a travel ban, an expanded list of people, organisations and companies subject to an asset freeze - including the Revolutionary Guards and the state-owned Bank Sepah - as well as an arms embargo and trade restrictions. Russia and China, however, have strong reservations, and any decision needs a consensus .

In a related development, the Syrian president, Bashar al-Assad, yesterday met the Iranian defence minister, Mostafa Najjar, to discuss military links between the two countries.

Syria is Iran's only Arab ally at a time of deepening confrontation between Arab states and Tehran. The two countries both support the Lebanese movement Hizbullah and the Palestinian Hamas while Iran has close links to Shia parties in Iraq. Syria has been improving its arsenal since last summer's war between Hizbullah and Israel while Iran has been upgrading its military capabilities.